Mathematics > Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

In a class of 80 seniors, there are 3 boys for every 5 girls. In the junior class, there are 3 boys for every  2 girls. If the two classes combined have an equal number of boys and girls, how many students are in the junior class?

(A) 72
(B) 80
(C) 84
(D) 100
(E) 120

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The Correct answer is E.

Explanation

Among the  seniors, there are  boys for every  girls, so  of the seniors, or , are boys and , or , are girls. Among the juniors,  are boys and  are girls. If  stands for the total number of juniors, then  are boys and  are girls. The total number of senior and junior boys is . The total number of senior and junior girls is . The question states that these quantities are equal, so . Solving this gives , or .